Dean loves blue shirts. This one has large brown buttons. It has two breast pockets but only the one on the right has a flap.
In Scarecrow (1x11), Dean is wearing it when he talks to the professor and subsequently gets captured by the townspeople and tied to a tree in the orchard. (I originally thought this jacket only appeared starting in S3, but it’s since been brought to my attention that it first appeared in Scarecrow! I’m not infallible, apparently.)
Dean wears it for the entirety of The Kids Are Alright (3x02).
In Long Distance Call (3x14), this might be the shirt Dean wears at the beginning when he and Sam are at the university and he gets the call from Bobby about the hunt.
This might be the shirt that Dean wears in Wishful Thinking (4x08), when Dean and Sam go talk to Wes and Dean gets into a fight with the mighty Todd.
In On The Head Of A Pin (4x16), Dean wears it from the beginning of the episode until he ends up in the hospital.
In The Rapture (4x20), this might be the shirt that Dean wears from when they find Jimmy in the warehouse until he escapes.
In My Bloody Valentine (5x14), Dean is wearing it when he and Sam open the soul-briefcase until after Sam defeats Famine.
In 99 Problems (5x17), Dean, ironically or poetically, wears this shirt when he talks to Lisa at the end of the episode.
In Point of No Return (5x18), Dean wears this shirt for the entire episode.
In Two Minutes to Midnight (5x21), Dean starts wearing this shirt when they are getting ready to go after Death. He wears it until after he successfully gets Death’s ring.
In Live Free or Twi-Hard (6x05), Dean wears this shirt when he and Sam go to check out the Black Rose bar. He keeps it on through his vampire ordeal, including his visit with Lisa. He changes out of it after he is returned to being human.
In You Can’t Handle the Truth (6x06), Dean wears this shirt at the very beginning of the episode, when he and Sam are in the park and Dean talks to Bobby on the phone.
In Meet the New Boss (7x01), Dean is wearing this shirt while drinking and watching cartoon porn, after their mostly-failed meeting with Death. He keeps it on for the remainder of the episode.
Dean is still wearing this shirt as Hello, Cruel World (7x02) opens, and until Castiel disappears into the water.
In Plucky Pennywhistle’s Magical Menagerie (7x14), Dean wears this shirt from when he and Sam are researching at the motel and then go to Plucky’s so that Sam can interrogate the staff, until the end of the episode.
In Reading is Fundamental (7x19), this might be the shirt that Dean wears for the entire episode.
In Everybody Hates Hitler (8x13), this might be the shirt that Dean wears when he, Sam, Aaron, and the golem break into the library, and Sam is attacked by the necromancer.
In Man’s Best Friend With Benefits (8x15), this might be the shirt that Dean wears at the beginning of the episode when he and Sam arrive at the motel and Portia shows up to tell them the situation.
In Freaks and Geeks (8x18), Dean wears this shirt at the end of the episode when saying goodbye to Krissy.
In The Purge (9x13), Dean wears this shirt at the beginning of the episode when he and Sam are in the bunker and Dean shows Sam the news article that leads them to the case.